Heat exchanger

ABSTRACT

A heat exchanger includes plural laminated tubes through which a coolant from a fuel cell flows, fins arranged between the tubes and at outermost sides in a lamination direction of the tubes, core plates connected to longitudinal end portions of the tubes, and tank members attached to the core plates to form tank spaces. The tubes are made of a first insulating material, and the fins and the core plates are bonded to the tubes by using metal parts provided separately from each other on surfaces of the tubes. In addition, a coating portion is coated with a second insulating material on surfaces of the core plates at least at an exposed position of the core plates and at positions around brazing portions of the core plate bonded to the tubes. Accordingly, the heat exchanger can be insulated from the fuel cell without using an electrical insulating liquid.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is based on Japanese Patent Application No. 2003-161045 filed on Jun. 5, 2003, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to a heat exchanger for cooling a fuel cell of a fuel-cell powered vehicle. In the heat exchanger, cooling water can be used as a coolant.

BACKGROUND OF THE INVENTION

[0003] In a cooling system of a fuel cell described in JP-A-2002-33108 (corresponding to US Patent Application Publication 2002/31693), a radiator (heat exchanger) is provided in a coolant circulation passage through which a coolant is circulated in the fuel cell. Further, as the coolant, an electric insulation liquid material is used. For example, the electric insulation liquid material is fluorinert (Sumitomo 3M make) of a fluoride inet liquid or an insulating oil. Furthermore, an insulating material is interposed between the fuel cell and the coolant circulation passage, or the coolant circulation passage is formed from an insulating material, so that the radiator is electrically insulated from the fuel cell.

[0004] However, the electrical insulating liquid such as the fluorinert has a low electrical conductivity as compared with a general coolant such as water and ethylene glycol. Therefore, it is difficult to sufficiently improve cooling performance in the radiator. Further, manufacturing cost of the cooling system of the fuel cell is increased because the electrical insulating liquid such as the fluorinert is expensive as compared with the general coolant.

[0005] Each component of the radiator may be formed by an insulation material in order to provide the insulating performance in the radiator while the general coolant is used. However, in this case, heat conductivity of the radiator is greatly deteriorated, and it is difficult to obtain a necessary cooling capacity in the radiator.

SUMMARY OF THE INVENTION

[0006] In view of the above-described problems, it is an object of the present invention to provide a heat exchanger which can be insulated from a fuel cell without using an electrical insulating liquid as the coolant while cooling performance of the heat exchanger is not largely deteriorated.

[0007] According to the present invention, a heat exchanger includes a plurality of tubes through which a coolant from a fuel cell flows to perform heat exchange, a plurality of fins arranged between adjacent the tubes and outermost sides of the tubes in a lamination direction of the tubes to be bonded to the tubes, a core plate connected to one longitudinal end portion of each tube, and a tank member made of resin. The tubes are made of a first insulating material, the tank member is attached to the core plate at a side opposite to the tubes with respect to the core plate, and the tank member and the core plate are attached to form a tank space communicating with the tubes. In the heat exchanger, the tubes have a plurality of metal parts separated from each other on outer surfaces of the tubes, and the fins and the core plate are bonded by brazing to the outer surfaces of the tubes at the metal parts. Because the metal parts are separated from each other on the outer surfaces of the tubes, it is possible to electrically insulate the fins and tube parts connected to the fins in the heat exchanger, even when a water-included liquid is used as the coolant. In addition, heat exchanging performance can be improved by the fins made of a metal material.

[0008] Preferably, a coating portion is coated by a second insulating material on one surface of the core plate opposite to the tank space. Generally, the core plate has an exposed portion exposed to outside from the tubes (side plates), and brazing portions brazed to the tubes. In this case, the coating portion is provided at least on the exposed portion and at positions around the brazing portions of the core plate. Accordingly, the insulating performance on the outer side of the heat exchanger can be effectively improved even when cooling water is used as the coolant.

[0009] In the heat exchanger, first and second side plates are generally arranged at the outermost fins in the lamination direction for reinforcing to extend in a longitudinal direction of the tubes. In this case, at least one longitudinal end portion of each side plate is made of the first insulating material. Furthermore, the one longitudinal end portion of each side plate has a brazing portion brazed to the core plate through a metal part provided on a surface of the longitudinal end portion of each side plate, and the coating portion is provided at a position around the brazing portion of each side plate. Therefore, the outside of the heat exchanger can be accurately insulated from the fuel cell.

[0010] More preferably, the brazing portion of the longitudinal end portion of each side plate is separated from positions where the tubes are brazed to the core plate. In this case, the insulating performance of the side plate can be improved.

[0011] According to the present invention, a first metal part bonded to the fins and a second metal part bonded to the core plate are provided on the outer surface of each tube to be separated from each other on the outer surface of each tube. Therefore, an uncovered part made of the first insulating material is formed on the surface of each tube between the second metal part and the first metal part. Accordingly, the insulating performance of the heat exchanger can be readily improved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings, in which:

[0013]FIG. 1 is a schematic diagram showing a fuel cell system including a fuel cell and a radiator (heat exchanger) according to a preferred embodiment of the present invention;

[0014]FIG. 2 is a front view showing the radiator in FIG. 1; and

[0015]FIG. 3 is a cross-sectional view showing a main portion of the radiator according to the embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016] A preferred embodiment of the present invention will be now described with reference to FIGS. 1-3. A fuel cell system shown in FIG. 1 includes a fuel cell 10 mounted on a fuel-cell powered vehicle, and a radiator 100 for cooling the fuel cell 10. A driving motor for running the vehicle is driven by using the fuel cell 10 as an electrical source. The radiator 100 cools coolant (cooling water) circulating in the fuel cell 10, so that temperature of the fuel cell is controlled.

[0017] The fuel cell 10 is constructed with fuel cell stacks composed of plural cells, and outer casings for accommodating the fuel cell stacks. Each of the cells of the fuel cell stack is formed by inserting an electrolyte film between a plus electrode and a minus electrode so as to generate electrical power by chemical reaction between hydrogen and oxygen.

[0018] As shown in FIG. 1, a radiator circulation passage 20 made of an insulating material is connected to the outer casing of the fuel cell 10 at two positions. For example, the radiator circulation passage 20 is defined by a rubber hose made of an insulating rubber material. The radiator 100 and a water pump 21 are arranged in the radiator circulation passage 20 in this order in a coolant flow direction. By the operation of the water pump 21, the coolant in the outer casing of the fuel cell 10 circulates in the radiator circulation passage 20 and the radiator 100 as in the arrows in FIG. 1. The coolant is an antifreeze liquid obtained by mixing ethylene glycal into water, for example. This antifreeze liquid is generally used as the coolant in a general gasoline-engine vehicle.

[0019] A bypass passage 22 through which the coolant bypasses the radiator 100 is provided in the radiator circulation passage 20 to be parallel to the radiator 100. The bypass passage 22 is defined by a rubber hose made of an insulating rubber material, for example. A valve 23 is provided at a join portion where the radiator circulation passage 20 at a downstream side of the radiator 100 and a downstream side of the bypass passage 22 are joined. The operation of the valve 23 is controlled by a control unit (not shown), so that a flow ratio between a coolant amount passing through the radiator 100 and a coolant amount passing through the bypass passage 22 can be adjusted. The valve 23 may be provided in a joint portion where the radiator circulation passage 20 at an upstream side of the radiator 100 and an upstream side of the bypass passage 22 are joined.

[0020] A reserve tank 24 is provided in the radiator 100 to absorb a volume expansion part of the coolant when the temperature of the coolant increases, and to supply a volume contraction part of the coolant to the radiator 100 when the temperature of the coolant decreases.

[0021] The radiator 100 includes a core portion 130, an upper tank member 110 and a lower tank member 120. The radiator 100 is vertical flow type in which coolant flows in tubes 131 of the core portion 130 vertically. For example, in FIGS. 2 and 3, the coolant flows through the tubes 131 downwardly from the upper tank member 110 toward the lower tank member 120. The core portion 130 is constructed with the plural flat tubes 131, plural fins 132, two side plates 133 and two upper and lower core plates 134.

[0022] Each of the fins 132 is a corrugated fin formed into a wave shape by bending a thin plate. The tubes 131 and the fins 132 are alternately stacked (laminated) in a lamination direction. The side plates 133 are attached to outermost fins 132 (right and left outermost sides in FIG. 2) of the stacked member to reinforce the core portion 130. The side plates 133 are attached to extend in a longitudinal direction of the tubes 131.

[0023] Each of the core plates 134 is provided with tube holes 134 a in which one end portions of the tubes 133 are inserted, and side plate holes 134 b in which one end portions of the side plates 133 are inserted. In addition, the core plates 134 have tank insertion portions 134 c at its outer peripheral portion, in which outer peripheral portions of the upper and lower tank member 110, 120 are inserted so that tank spaces communicating with the tubes 131 are formed. Furthermore, plural claw portions 134 d for fastening the upper and lower tank members 110, 120 are provided in the core plate 134 at outer sides of the tank insertion portions 134 c.

[0024] The upper tank member 110 and the lower tank member 120 are made of a resin material such as a nylon material including glass fiber, to have a heat resistance and a sufficient strength. Each of the upper tank member 110 and the lower tank member 120 is formed into an approximate U shape in cross section. An open end of the tank member 110, 120 faces the core plate 134, and is connected to the core plate 134 to form the tank space.

[0025] As shown in FIG. 3, a seal member 140 (seal packing) is inserted between the outer peripheral portion of each tank member 110, 120 around the opening side of each tank member 110, 120 and the tank insertion portion 134 c of the core plate 134, and each tank member 110, 120 is mechanically connected to each core plate 130 by using claws 134 d.

[0026] An inlet pipe 111, a coolant filling port 112 and attachment portions 113 are provided in the upper tank member 110 integrally with the upper tank member 110. In contrast, an outlet pipe 121 and attachment portions 122 are provided in the lower tank member 120 integrally with the lower tank member 120. The inlet pipe 111 through which the coolant in the radiator circulation passage 20 flows into the upper tank member 110 of the radiator 100 is connected to the radiator circulation passage 20, and the outlet pipe 121 through which the coolant in the lower tank member 120 is discharged to the radiator circulation passage 20 is connected to the radiator circulation passage 20. Accordingly, coolant in the radiator circulation passage 20 flows into the upper tank member 110 from the inlet pipe 111, flows through the tubes 131 of the core portions 130, and is collected into the lower tank member 120. Then, the coolant collected into the lower tank member 120 flows out of the radiator 100 through the outlet pipe 120.

[0027] Next, the main portion of the present invention will be now described. In this embodiment, the fins 132 and the core plate 134 are made of a general heat conductive material (metal material) such as an aluminum or an aluminum alloy. The tubes 131 and the side plates 133 are made of a ceramic material (first insulating material) having electrical insulating performance. For example, the tubes 131 and the side plates 133 are made of a ceramic material having a high purity alumina as main material. Each of the tubes 131 and each of the side plates 133 are formed by burning after being molded by extrusion. When the dimensions of the tubes 131 and the side plates 133 cannot be accurately set only by the burning, polishing can be performed after the burning, if necessary.

[0028] The surface of each tube 131 can be provided with a first metal part 131 a around the tube holes 134 a of the core plate 134, and a second metal part 131 b contacting fins 132. The metal parts 131 a, 131 b are formed by providing a metal layer on the ceramic surface of the tubes 131. The metal parts 131 a, 131 b can be formed on the ceramic surface by a direct or an indirect metalization method or a melting connection method. Further, an Al—Si type brazing material can be formed on the top surfaces of the metal parts 131 a, 131 b in order to readily bond the tubes 131 with the fins 132 and the core plates 134. The metal parts 131 a, 131 b are provided on the outer surface of the tubes 131 made of the ceramic material to be separated from each other. Therefore, the outer surface of each tube 131 has uncovered portions (exposed portions) without the metal parts 131 a, 131 b between the metal parts 131 a and 131 b. In addition, the metal parts 131 b are provided on the outer surface of each tube 131 to be separated from each other to have the uncovered portion between the metal parts 131 b, and the metal parts 131 a are provided on the outer surfaces of the tubes 131 to be separated from each other.

[0029] The surface of each side plate 133 can be provided with first metal parts 133 b contacting the outermost fin 132, and second metal parts 133 a around the side plate holes 134 b of the core plates 134. Similarly to the tubes 131, the first metal part 133 b is provided on the outer surface of the side plate 133 to be separated from the second metal parts 133 a. In addition, the second metal part 133 a provided on the outer surface of the side plate 133 is separated from the metal part 131 a provided on the outer surface of each tube 131.

[0030] By the metal parts 131 a, 131 b, 133 a and 133 b, the tubes 131 can be brazed to the core plates 134 and the fins 132, respectively, and the side plates 133 can be brazed to the core plates 134 and the fins 132, respectively, in the core portion 130.

[0031] Furthermore, a coating portion 150 is coated by a resin material (second insulating material) onto the outer surface of the core plate 134 at least at the exposed portion and positions around the brazing portions the core plate 134, where the tubes 131 and the side plates 133 are inserted to be brazed to the core plate 134. Hear, the exposed portion is the part of the core plate 134 exposed to outside from the side plates 133 and the tubes 131. For example, the coating portion 150 is resin-coated by using a silicon material (second insulating material). As shown in FIG. 3, the coating portion 150 is coated at the outside surface opposite to the tank space of the tank member 120, 130.

[0032] In the fuel cell 10, electrical power is generated by the chemical reaction between hydrogen and oxygen supplied to both the electrodes. Heat generated during the electrical power generation is transmitted to the coolant (cooling water), and flows into the radiator 100 by the operation of the water pump 21 through the radiator circulation passage 20. The coolant flowing through the radiator 100 is cooled, and the cooled coolant is circulated to the fuel cell 10, so as to control the temperature of the fuel cell 10. When a generated electrical power amount of the fuel cell 10 is small, the coolant from the fuel cell 10 flows through the bypass passage 22 while bypassing the radiator 100, by the operation of the switching valve 23. Hear, the flow amount of the coolant flowing through the radiator 100 is adjusted, so that the temperature of the fuel cell 10 during the operation of the fuel cell 10 can be controlled in a suitable temperature range. Generally, the radiator 100 cools the coolant to be equal to or lower than a predetermined temperature (e.g., 80° C.).

[0033] When the power generation operation of the fuel cell 10 is performed, a high voltage is applied to the coolant (cooling water). In this embodiment, the tubes 131 and the side plates 133 are made of an insulating material such as the ceramic material. Furthermore, the metal parts 131 b on the surfaces of the tubes 131, to be bonded to the fins 132, are separated from the metal parts 131 a bonded to the core plate 134, and the metal parts 133 b on the surfaces of the side plates 133, to be bonded to the fins 132., are separated from the metal parts 133 a bonded to the core plate 134. In addition, the coating portion 150 made of an insulating material is provided on the outer surface of the core plate 134 at the exposed portions of the core plates 134, exposed to an outside, and the portions around the brazing portions (bonding portions) of the core plates 134, where the tubes 131 and the side plates 133 are brazed to the core plates 134. Thus, even when the high-voltage coolant flows in the radiator 100, the high-voltage coolant can be insulated from the outside of the radiator 100. Thus, it is unnecessary to use the electrical insulation liquid as the coolant. Accordingly, cooling water can be used as the coolant in the radiator 100.

[0034] In this embodiment, the tubes 131 and the side plates 133 can be bonded to the fins 132 made of a metal material such as aluminum or an aluminum alloy by brazing, using the metal parts 131 b, 133 b provided separately from each other on the outer surfaces of the tubes 131 and the side plates 133. Accordingly, even when the coating portion 150 is not provided at the positions around the brazing portions of the core plate 134, and even when the coolant such as the cooling water is used, the insulation of the fins 132 and the tubes 131 can be obtained.

[0035] Because the fins 132 contained in a large area in the radiator 100 do not need to be made of an insulating material while being insulated, heat transmitting performance in the radiator 100 can be improved, and cooling performance for cooling the coolant in the radiator 100 can be effectively improved.

[0036] Further, the side plates 133 are made of a ceramic material, and are bonded to the outermost fins 132 in the lamination direction, similarly to the tubes 131. Therefore, the radiator 100 can be reinforced while the coolant (cooling water) in the radiator 100 can be insulated from the outside of the radiator 100.

[0037] In this embodiment, even when any the tube 131 or the side plate 133 is not brazed to the core plate 134 to cause a non-bonding portion, the non-bonding portion is closed by the coating portion 150. Therefore, the coating portion 150 can be also used as a seal means between the tubes 131, the side plates 133 and the core plates 134.

[0038] (Other Embodiments)

[0039] Although the present invention has been fully described in connection with the preferred embodiment thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.

[0040] For example, in the above-described embodiment, the side plate 133 can be formed to have a first portion made of a ceramic material and a second portion made of an aluminum material. Hear, the first portion is a portion around a brazing portion brazed with the core plate 134, and the second portion is the other portion of the side plate 133 except for the first portion. In this case, the metal part 133 b provided on the side plate 133 described in the above embodiment can be omitted.

[0041] Further, for example, when the heat exchanger is assembled to a vehicle while an outer portion of the core plate 134 is covered by an insulation member, the outer surface of the heat exchanger can be insulated with respect to the coolant even when the coating portion 150 is not provided.

[0042] In the above-described embodiment of the present invention, the coating portion 150 (coating layer) is coated on the core plate 134 at positions around the bonding portions of the core plate 134 where the longitudinal end portions of the tubes 131 are bonded to the core plate 134. However, in the present invention, because the metal parts 131 a on the tubes 131 are provided to be separated from the metal parts 131 b on the tubes 131, the coating portion 150 provided at positions around the tube bonding portions of the core plate 134 can be omitted. Further, the metal parts 131 b on the tubes 131, to be bonded to the fins 132, are separated from metal part 131 a on the tubes 131, to be bonded to the core plate 134. Therefore, the ceramic surfaces of the tubes 131 are exposed outside between the metal parts 131 b and the metal parts 131 a. Accordingly, the fins 132 and the main parts of the tubes 131 connected to the fins 132 can be electrically insulated.

[0043] In the above-described embodiment, the present invention is typically applied to the heat exchanger having the upper and lower tank members 110, 120 and the upper and lower core plates 134. However, the present invention can be applied to a heat exchanger only having one side tank and one side core plate. Further, in the above-described embodiment, the upper and lower tank members 110, 120 and the core plates 134 extend approximately horizontally. However, the present invention can be applied to a heat exchanger where the tank members 110, 120 and the core plates 134 extend approximately vertically or extend in a direction crossing with the horizontal direction.

[0044] Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims. 

What is claimed is:
 1. A heat exchanger comprising: a plurality of tubes through which a coolant from a fuel cell flows to perform heat exchange, the tubes being laminated in a lamination direction and made of a first insulating material; a plurality of fins arranged between adjacent the tubes and outermost sides of the tubes in the lamination direction to be bonded to the tubes; a core plate connected to one longitudinal end portion of each tube; and a tank member made of resin, the tank member being attached to the core plate at a side opposite to the tubes with respect to the core plate, wherein the tank member and the core plate are attached to form a tank space communicating with the tubes, wherein: the tubes have a plurality of metal parts separated from each other on outer surfaces of the tubes; and the fins and the core plate are bonded by brazing to the outer surfaces of the tubes at the metal parts.
 2. The heat exchanger according to claim 1, further comprising a coating portion coated by a second insulating material on one surface of the core plate opposite to the tank space wherein: the core plate has an exposed portion exposed to outside from the tubes, and brazing portions brazed to the tubes; and the coating portion is provided at least on the exposed portion and at positions around the brazing portions of the core plate.
 3. The heat exchanger according to claim 2, further comprising first and second side plates arranged at the outermost fins in the lamination direction for reinforcing to extend in a longitudinal direction of the tubes, wherein: at least one longitudinal end portion of each side plate is made of the first insulating material; the one longitudinal end portion of each side plate has a brazing portion brazed to the core plate through a metal part provided on a surface of the longitudinal end portion of each side plate; and the coating portion is provided on the core plate at a position around the brazing portion of each side plate.
 4. The heat exchanger according to claim 1, further comprising first and second side plates arranged at the outermost fins in the lamination direction for reinforcing to extend in a longitudinal direction of the tubes, wherein: at least one longitudinal end portion of each side plate is made of the first insulating material; the one longitudinal end portion of each side plate has a brazing portion brazed to the core plate through a metal part provided on a surface of the longitudinal end portion of each side plate; and the brazing portion of the longitudinal end portion of each side plate is separated from positions where the tubes are brazed to the core plate.
 5. The heat exchanger according to claim 1, further comprising first and second side plates arranged at the outermost fins in the lamination direction for reinforcing to extend in a longitudinal direction of the tubes, wherein: all the side plates are made of the first insulating material; and each of the side plates further has a first metal part provided on its surface to be bonded to the outermost fin, and a second metal part provided separately from the first metal part on its surface to be bonded to the core plate.
 6. A heat exchanger comprising: a plurality of tubes through which a coolant from a fuel cell flows to perform heat exchange, the tubes being laminated in a lamination direction and made of a first insulating material; a plurality of fins arranged between adjacent the tubes and outermost sides of the tubes in the lamination direction to be bonded to the tubes; a core plate connected to one longitudinal end portion of each tube; a tank member made of resin, the tank member being attached to the core plate at a side opposite to the tubes with respect to the core plate, wherein the tank member and the core plate are attached to form a tank space communicating with the tubes; a plurality of first metal parts provided on outer surfaces of the tubes to be bonded to the fins; and a plurality of second metal parts provided on the outer surfaces of the tubes to be bonded to the core plate, wherein the second metal parts are provided on the outer surfaces of the tubes to be separated from the first metal parts.
 7. The heat exchanger according to claim 6, wherein: the first metal parts are provided on the outer surfaces of the tubes to be separated from each other; and the second metal parts are provided on the outer surfaces of the tubes to be separated from each other.
 8. The heat exchanger according to claim 6, wherein the first metal part and the second metal part are provided on the surface of each tube to cover a part of the outer surface of each tube and to have an uncovered part between the second metal part and the first metal part.
 9. A heat exchanger comprising: a plurality of tubes through which a coolant from a fuel cell flows to perform heat exchange, the tubes being laminated in a lamination direction and made of a first insulating material; a plurality of fins arranged between adjacent the tubes and outermost sides of the tubes in the lamination direction to be bonded to the tubes; a core plate connected to one longitudinal end portion of each tube; a tank member made of resin, the tank member being attached to the core plate at a side opposite to the tubes with respect to the core plate, wherein the tank member and the core plate are attached to form a tank space communicating with the tubes; a first metal part provided on an outer surface of each tube to be bonded to the fins; and a second metal part provided on the outer surface of each tube to be bonded to the core plate to have an uncovered part on the surface of each tube between the second metal part and the first metal part.
 10. The heat exchanger according to claim 1, wherein the first insulating material is a ceramic material.
 11. The heat exchanger according to claim 1, wherein the core plate and the fins are made of a metal material.
 12. The heat exchanger according to claim 1, wherein the tank member and the core plate are arranged at both the longitudinal end portions of each tube to form the tank space at two longitudinal sides of the tubes. 